Composition-driven structural and magnetic transitions in mechanically activated (1−x)BiFeO3-(x)BaTiO3 solid solutions

This work presents systematic investigations of the structure and magnetic properties of mechanically activated (1−x)BiFeO3-(x)BaTiO3solid solutions in a wide range of constituents concentration (x=0.1-0.9). X-ray diffraction and Mössbauer spectroscopy were used as complementary methods in order to control the mechanical activation process and to follow composition-driven structural transition from rhombohedral to cubic symmetry. The investigations revealed that the structural transformation proceeds for x=0.4 and is accompanied by the disappearance of magnetic ordering in the samples. Moreover, evolution of the hyperfine interactions parameters with composition of the solid solutions was discussed in details. In particular, it was shown that hyperfine magnetic field induction decreases due to decreasing energy of superexchange interaction of iron ions. For the paramagnetic samples with x≥0.4 gradual decrease of quadrupole splitting was detected. Scanning electron microscopy was used to analyze microstructure of the samples and showed that the average grain size is in the range of 200-300 nm.